<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #outer{
            background-image: url("mi01.webp");
            height: 500px;
            background-size: cover;
        }
        #inner{
            width: 200px;
            height: 500px;
            /* background-color: #000;
            opacity: 0.4;
            color: wh; */
            background-color: rgba(0, 0, 0, 0.4);
            color: #e3e3e3;
        }
    </style>
</head>
<body>
    <div id="outer">
        <div id="inner">
            透明背景
        </div>
    </div>
</body>
</html>